<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
</head>
<body>


<div id="app">
    <input type="text" v-on:input="changeTitle">
  <p>{{ title}}</p>
  
</div>
<script src="https://unpkg.com/vue/dist/vue.js"></script>
<script type="text/javascript">

new Vue({

el: '#app',
data:{

title: 'Hello World!'
},
methods: {

 changeTitle: function(event){
   this.title =  event.target.value;
 }
}

})

</script>


</body>

</html>